Field of the Invention
The present invention relates to a power-module substrate configuring a power module controlling a large electric current and a large voltage and a manufacturing method thereof.
Priority is claimed on Japanese Patent Application No. 2012-77401, filed Mar. 29, 2012, the content of which is incorporated herein by reference.
Description of the Related Art
Conventionally, as a semiconductor device controlling a large electric current and a large voltage, a power module having a structure in which electronic components such as a semiconductor chip and the like are mounted on a power-module substrate is known. As a manufacturing method of the power module, for example, methods described in Patent Document 1 and Patent Document 2 are known. In these methods: a metal plate being a circuit layer is stacked on one surface of a ceramic substrate interposing brazing material; a metal plate being a heat-radiation layer is stacked on the other surface of the ceramic substrate interposing the brazing material; and those are pressed in a stacking direction and heated so as to bond the metal plates to the ceramic substrate, so that a power-module substrate is manufactured. Subsequently: a top plate part of a heat sink is stacked on a surface of the heat-radiation layer that is opposite to the surface to which the ceramic substrate is bonded interposing the brazing material; and the heat-radiation layer and the heat sink are pressed in this stacking direction and heated so as to bond to each other, so that a power-module substrate with a heat sink is manufactured.
For a bonding method of the metal plate of the power-module substrate and the heat sink, vacuum brazing, soldering, screw clamping, brazing using flux, and the like are applied.
In Patent Document 3, as a bonding method of a top plate of a heat sink and a metal plate of a power-module substrate, it is described to braze with spreading flux. This brazing is a method of bonding by removing oxide on a brazing face by spreading fluoride-based flux on the brazing face and heating in non-oxidizing atmosphere, in which expensive equipment is not necessary and it is comparatively easy to braze stably.